Pictured above: Ken Pecota, left, and Craig Yencho at the 2008 Sweetpotato Field Day.
October 2008
When it comes to deciding what sweetpotato variety to plant, North Carolina growers increasingly are choosing the new variety Covington.
Covington, a sweetpotato variety developed by sweetpotato breeders Dr. Craig Yencho and Kenneth Pecota, associate professor and researcher, respectively, in the Department of Horticultural Science in the North Carolina State University College of Agriculture and Life Sciences, was released, or made available to growers, in 2005. Since then, it has rapidly found favor with the state’s sweetpotato growers.
Boxes of Covington sweetpotatoes on display during the 2008 Sweetpotato Field Day.
“Covington is the dominant variety produced in North Carolina,” says Yencho. “It accounts for 75 to 80 percent of our total acreage.” Yencho adds that in California, Covington is rapidly displacing a variety called Beauregard, which has been the most widely grown orange-flesh sweet potato in that state.
Why Covington?
“The growers like it because it produces a more stable crop,” Yencho says. “It produces good, uniform yields, year in and year out. The other thing that growers really like is that it has an exceptionally high pack out.”
Pack out refers to the percentage of USDA Grade Number 1 sweetpotatoes that growers ship to consumers after they have been graded and sorted from storage. Growers typically store their sweetpotatoes in warehouses where the temperature and humidity are controlled (see A Sweetpotato Storage Story: Negative Horizontal Ventilation is Positive for Sweetpotato Growers, http://www.cals.ncsu.edu/agcomm/difference/sweetpotatoes/storage.html).
Given the right temperature and humidity, sweetpotatoes can be stored up to 10 months. Storage allows growers to sell throughout the year rather than be confined to a narrow market window.
In field tests of Covington, Yencho says he typically sees a 60 to 70 percent pack out of number one sweetpotatoes. Number one sweetpotatoes are the premium grade that go to supermarket shelves and demand the highest price.
“Growers will tell you they’re getting 80 to 90 percent pack out,” Yencho adds. “Compare that to Beauregard, which is often less than 50 percent, and that turns into dollars and cents for growers.”
Covington has also helped growers take advantage of a growing export market to Europe. After packing and sorting, Covington also yields good amounts of a sweetpotato size class that is slightly smaller in size and shape than U.S. No. 1 and that Europeans prefer, Yencho says. Covington has a long shelf life, so it’s better able to survive transport, and takes bumps and bruises better.
For now, Covington appears to be king, but it’s reign may be short-lived, for on the horizon is another variety developed by Yencho and Pecota and their cooperators that may also find favor with growers. For now, it’s known only by a code: NC99-573. In the near future, it will get a name and be released, says Yencho.
Yencho says NC99-573 has very high yield and “pretty good pack out, comparable but not quite as good as Covington.” The new variety may be planted and harvested earlier in the growing season than most others and produces very uniform sweetpotatoes with good flavor.
“It will be interesting to see how 573 and Covington fit together in our sweetpotato production system,” Yencho says. “My gut feeling is that they’re complimentary.”
He adds, “You can plant 573 early. Covington takes a little longer to produce plants, so you can get your 573s planted, then you can come behind that with Covington. I think Covington is going to be more amenable to processing, whereas 573 is going to be more amenable to table stock (supermarkets) and maybe canning.”
Yencho says 573 is susceptible to root knot nematodes, while Covington resists nematodes. And Covington has some insect resistance, which 573 does not have.
When a new variety becomes available, growers usually have to make a choice between the new kid on the block and older varieties. But if Yencho is correct and Covington and 573 are complimentary, growers may be able to take advantage of both varieties.
- Dave Caldwell
